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filemap: Update the folio_mark_dirty documentation

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The previous comment was not terribly helpful.  Be a bit more explicit
about the necessary locking environment.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2022-04-28 14:21:02 -04:00
parent cd125eeab2
commit 2ca456c248
1 changed files with 6 additions and 4 deletions
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10
mm/page-writeback.c
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@ -2602,10 +2602,12 @@ EXPORT_SYMBOL(folio_redirty_for_writepage);
* folio_mark_dirty - Mark a folio as being modified.
* @folio: The folio.
*
* For folios with a mapping this should be done with the folio lock held
* for the benefit of asynchronous memory errors who prefer a consistent
* dirty state. This rule can be broken in some special cases,
* but should be better not to.
* The folio may not be truncated while this function is running.
* Holding the folio lock is sufficient to prevent truncation, but some
* callers cannot acquire a sleeping lock. These callers instead hold
* the page table lock for a page table which contains at least one page
* in this folio. Truncation will block on the page table lock as it
* unmaps pages before removing the folio from its mapping.
*
* Return: True if the folio was newly dirtied, false if it was already dirty.
*/